Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author.

DRY MATTER PARTITIONING IN Zantedeschia K. Spreng, AS INFLUENCED BY TE:MPERA TURE AND PHOTOSYNTHETIC

PHOTON FLUX

Keith Alien Funnell 1993

A thesis presented in partial · fulfilment of the requirements

for the degree of Doctorate of Philosophy in

Horticultural Science at Massey University

11

ABSTRACT

The in vivo and in vitro dry matter accumulation and partitioning in plants of the

Zantedeschia pentlandii-like (Watson) Wittm. selection 'Best Gold' were described under

a range of either temperature and photosynthetic photon flux (PPF) regimes, or sucrose

concentrations, using plant growth analysis.

The initiation of tuber growth, as denoted by increases in both structural and starch dry

weights, did not require an obligative environmental trigger.

Relative rates of dry matter accumulation (RGRw) increased linearly with increasing

temperature up to ·a maximum of 28 C, with maximum final total and tuber dry weight

occurring between 21 and 26 C both in vivo and in vitro. The linear relationship between

the relative rate of dry matter accumulation of the tuber (RGRT) and temperature, indicated

a PPF dependent base temperature for tuber growth between 4 .8 and 6. 1 C .

By principally altering dry matter partitioning, total dry matter accumulation was highly

adaptive to PPF regime. The ability to alter the photosynthetic rate and the partitioning

of the daily increment of dry matter into leaf area (LWP), resulted in greater values of the

estimated final total plant dry matter under the low PPF regime (348 l-'mol·m-2·s-1), at

temperatures less than 22 C. At temperatures greater than 19 C the estimated maximum

to� plant dry weight was either not influenced by PPF or was slightly greater under the

high PPF regime (694 l-'mol·m-2·s-1). This ability to effectively utilize a low PPF regime

indicates that this selection is shade tolerant. The optimum PPF for growth was found to

be temperature dependent: estimated maximum total plant dry weight occurred under high

PPF at 25 C, whereas the estimated maximum tuber dry weight occurred at 24.5 C under

low PPF.

RGRw was highly correlated with LWP. In contrast, only a poor correlation was

determined between RGRw, and either the efficiency of these leaves to produce additional

dry matter, i.e., net assimilation rate (NAR), or starch concentration or soluble

carbohydrate concentration. Photosynthetic rate was correlated with RGRw, but not with

RGRT. While the photosynthetic process must be involved in contributing photoassimilates

for tuber growth, it was suggested that the plant's response to dry matter partitioning into

the leaf, i.e., LWP, and the tuber, i.e., TWP, had a greater influence in determining tuber

growth than could be accounted for by the photosynthetic rate.

Mechanisms of acclimation under both PPF regime suggested that tuber growth was

principally source limited. Source limitation was expressed either in terms of:

111

1) enhanced �ntersink competition for assimilates, as occurred under the low

PPF regime, where enhanced leaf area development (LWP) was in direct

competition with enhanced tuber growth (RGRT). This was also confirmed

in vitro where dry matter partitioning to the tuber was reduced under limited

source strength.

2) efficiency of dry matter accumulation of leaf area present, as occurred under

the high PPF regime, where large increases in RGRT were correlated with

increased NAR. This was also confirmed in vitro where increased source

strength increased tuber dry weight.

However, in vitro experiments where source strength was controlled, illustrated that tuber growth was also potentially sink limited at temperatures both lower and higher than the

optimum. At 3 1 C the sink limitation of tuber growth arose from more than the

temperature-induced limitation on growth and respiration found at other sink limiting temperatures. At this temperature an additional form of sink limitation was evident where partitioning of dry matter towards the tuber was also restricted. It was suggested that this additional form of sink limitation may have arisen from high temperature inactivation of

starch metabolising or sucrose unloading enzymes.

Application of the dry matter partitioning term TWP, provided a more sensitive measure

of short term changes in partitioning than the conventionally used term, harvest index. \ ; '

The optimum temperature range for growth was close to the average daily air temperature

during the season for the sites of natural habitat of the suggested parent specie,

Zantedeschia pentlandii. Similarly the shade tolerance_ status of this selection was

paralleled by the diversity of PPF habitats it naturally occupies, as created by open

grassland and forest margins. It was therefore suggested that Zantedesclzia 'Best Gold'

is well adapted to optimise growth under the temperature and PPF regimes of its natural

habitat.

This study suggests that improvements in commercial yield of Zantedeschia tubers can be

achieved in all regions of N ew Zealand through the use of protected cultivation with

supplemental heating. However, unless using protected cultivation, the potential

improvements in commercial tuber yields, through the application of shading, are only

likely to be evident in warmer regions of N ew Zealand where growers utilize extended

periods of cultivation and optimise leaf area duration.

lY

ACKNOWLEDGEMENTS

The completion of this thesis is a piece of independent research, but so many individuals

have contributed either directly or indirectly. In panicular, I would like to the thank the

following:

my supervisors Dr I. J. Warrington, Dr J.A. Plummer and Dr E. W. Hewett for their

challenges, guidance and constructive criticism;

Dr D.J. Chalmers for his leadership and foresight as Head of Depanment of the

then Depanment of Honicultural Science, to initiate the unique opponunity for me

to study towards my PhD,·

the management and staff of HonResearch (formally DSIR Plant Physiology

Division, and DSIR Fruit and Trees) especially Dr D. Cohen, and the Depanment

of Plant Science (formally the Depanment of Honicultural Science) for the provision

of facilities and technical advice;

Massey University Research Fund (MURF), Massey University Agricultural

Research Fund (MUARF), and The C. Alma Baker Trust who all provided various

forms of financial contribution;

Dr J. M. Wilson for an endless supply of tubers and seed, as well as thought

provoking discussion;

my family and friends who either provided moral suppon or without knowing it,

suitable distractions that created some semblance of normality during a demanding

few years of my life.

Parts of Sections 1 , 3 , 4 and 5 of this thesis have been published in the following;

Funnell, K.A. 1993. Zantedeschia, p. 683-739. In: A. De Hertogh and M. Le N ard

(eds.). The physiology of flower bulbs. A comprehensive treatise on the

physiology and utilization of ornamental flowering bulbous and tuberous plants.

Elsevier Science Publishers, Amsterdam.

Funnell, K.A., J.A. Plummer and I.J. Warrington. 1990. Temperature and light effects

on tuber growth in calla lilies. Abstracts XXIII Intl. Hort. Congr., Firenze, Italy,

1990, no. 3261.

V

CO� PAGE

ABSTR.Acr . . • . • • . . • • . . . • • • • . • . . • . . . . . . . . • . . . . . . . . . . . . . n ACKNO�GEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. w co�s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v UST OF ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi NOTES ON CITATION FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii UST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv UST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii LIST OF PLATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiv

1 BOTANICAL, ECOLOGICAL, PHYSIOLOGICAL, AND HORTICULTURAL BACKGROUND OF THE GENUS Zantedeschia. 1

1.1 Introduction and overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 World production areas and volumes . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.3

I \ I i

Botanical classification, morphology, distribution and habitat 1. 3.1 Botanical classification and morphological description

. . . . . . . . . . 2

2

1.3.2 Distribution and climate of origin . . . . . . . . . . . . . . . . . . . . . . 5

1.4 ' Breeding: goals and specific problems . . . . . . . . . . . . . . . . . . . . . . . . 9

1.5 Vegetative growth and development . . . . . . . ... . . . . . . . . . . . . . . . . 1 1

1. 5 .1 General overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1

1.5.2 Influence of internal factors .................. : . . . . . . 1 1

1.5.2.1 Dormancy . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1

1.5.3 Influence of external factors . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.5.3.1 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.5.3.2 Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.5.3.3 Chemical growth regulators . . . . . . . . . . . . . . . . 13

1.5.3.4 Growing medium, irrigation, nutrition and weed control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.5.4 Commercial rhizome and tuber production . . . . . . . . . . . . . . . . 14

1.5.4.1 Goals and techniques . . . . . . . . . . . . . . . . . . . . 14

1.5.4.2

1.5.4.3

Planting to harvest requirements . . . . . . . . . . . . . 15

Postharvest storage and transport requirements . . . . 16

vi

1. 6 Control of flowering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7

1. 6 . 1 General overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7

1. 6 . 2 Flowering process and terminology . . . . . . . . . . . . . . . . . . . . 1 7

1. 6 . 3 Influence of internal factors . . . . . . . . . . . . . . . . . . . . . . . . . 2 0 1 . 6. 3 . 1 Rhizome and tuber size . • . • • • • • • • • • • • • . . . . 2 0 1. 6 . 3 . 2 Dormancy and floral induction . . . . . . . . . . . . . . 2 0

1. 6 . 4 Influence of external factors . . . . . . . . . . . . . . . . . . . . . . . . . 21 1. 6. 4 . 1 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . 21 1. 6 . 4 . 2 Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1. 6. 4 . 3 Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1. 6. 4 . 4 Chemical growth regulators . . . . . . . . . . . . . . . . 24 1. 6 . 4 . 5 Air pollutants . . . . . . . . . . . . . . . . . . . . . . . . . 26

1. 6 . 5 Commercial forcing for l>ot and cut flower production . . . . . . . . . 26 1. 6. 5 . 1 Rhizome and tuber storage . . . . . . . . . . . . . . . . . 26 1. 6 . 5 . 2 1. 6. 5 . 3 1. 6 . 5 . 4 1. 6 . 5 . 5 1 . 6 . 5 . 6 1 . 6 . 5 . 7

Pre-plant treatments . . . . . . . . . . . . . . . . . . . . . 26 Planting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Height control . . . . . . . . . . . . . . . . . . . . . . . . 27 Forcing environment . . . . . . . . . . . . . . . . . . . . 28 Physiological disorders . . . . . . . . . . . . . . . . . . . 28 Post-greenhouse handling and marketing . . . . . . . . 29

1. 7 Diseases and insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 I \ I

1. 8 Miscellaneous physiological and biochemical studies . . . . . . . . . . . . . . 3 1 1 .8 . 1 Spathe regreening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 1 .8 . 2 Tuber respiration . . . . . . . . . . . . . . . . -. . . . . . . . . . . . . . . 3 1

1.9 Concluding remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1

1. 1 0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2 INTRODUCTORY OVERVIEW AND AIM OF THE CURRENT STUDY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1

2. 1 Overview of study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1

2. 2 Aim of this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2

2. 3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3 DRY MA TIER -ACCUMULATION AND LEAF LAMINA

vii

DEVELOPMENT OF Zantedeschia 'Best Gold' IN RESPONSE TO TEMPERATURE AND PHOTOSYNTHETIC PHOTON FLUX . . . . . . . 4 5

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5

3.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.1 Cultural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.2 Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8 3.2.3 Experimental . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 49

3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 3. 3.1 Overview and initial eStablishment . . . . . . . . . . . . . . . . . . . . . 5 4 3. 3. 2 Repetition of treatments over years . . . . . . . . . . . . . . . . . . . . 5 7 3.3.3 Curve fitting of total plant dry weight . . . . . . . . . . . . . . . . . . . 5 7 3.3.4 Curve fitting of leaf area and dry weight . . . . . . . . . . . . . . . . . 61 3.3.5 Relationships between derived parameters . . . . . . . . . . . . . . . . 68

3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.4.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

3.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

4 TUBER DRY MATTER ACCUMULATION OF Zantedeschia 'Best Gold' IN RESPONSE TO TEMPERATURE AND PHOTOSYNTHETIC PHOTON FLUX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4 . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4 .2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4 .3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4 .3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4 .3.2 Commencement of tuber growth . . . . . . . . . . . . . . . . . . . . . . 91

4 . 3. 3 Curve fitting of tuber growth . . . . . . . . . . . . . . . . . . . . . . . . 9 2

4 .3.4 Maximum tuber weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6

4 .3.5 Base temperature for tuber growth . . . . . . . . . . . . . . . . . . . . . 9 6

viii

4. 3 . 6 Tuber and leaf weight partitioning . . . . . . . . . . . . . . . . . . . . . 9 7

4 . 3 . 7 Net assimilation rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 01

4 . 3. 8 Relationships between derived parameters . . . . . . . . . . . . . . . 1 02

4 . 4 Discussion . . . . . . . . . . . . . . · . . . . . . . . . . . . . . . . . . . . . . . . . 1 07 4 . 4 . 1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

4.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 2

5 PHOTOSYNTHETIC ACTIVITY OF Zmztedeschia 'Best Gold' IN RESPONSE TO TEMPERATURE AND PHOTOSYNTHETIC PHOTON FLUX 116

5 .1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

5.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 5 . 2.1 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

5.2.1.1 Photosynthesis as a function of leaf expansion . . . . 119 5.2.1. 2 Photosynthetic rate as a function of duration from

commencement of daily lighting . . . . . . . . . . . . 119 5.2.1.3

5.2.1.4

Photosynthetic rate as a function of photosynthetic photon flux . . . . . . . . . . . . . . . . . . . . . . . . . 120 Photosynthesis during plant development . . . . . . . 1 21

5. 3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

5.4

5.3 . 1 Photosynthesis as a function of leaf expansion . . . . . . . . . . . . . 122 5.3.2 Photosynthesis as a function of duration from commencement of

daily lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.3.3 Photosynthetic rate as a function of photosynthetic photon flux . . . 125 5.3.4 Photosynthesis during plant development . . . . . . . . . . . . . . . . 1 29 5.3 . 5 Photosynthesis as a predictor of growth and yield . . . . . . . . . . . 13 2

Discussion 13 3

5.5 References . . . . . . .... . � . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

6 CARBOHYDRATE CONCENTRATION OF Zantedeschia 'Best Gold' IN RESPONSE TO TEMPERATURE AND PHOTOSYNTHETIC PHOTON

ix

FLUX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

6.2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 6.2.1 Cultural and environmental . . . . . . . . . . . . . . . . . . . . . . . . 148 6.2.2 Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

6.2.2.1 Determination of concentration of specific soluble carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . 148

6.2.2.2 Starch and soluble carbohydrate concentration as a function of duration from commencement of daily lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.2.2.3 Starch and soluble carbohydrate concentration during plant development . . . . . . . . . . . . . . . . . 15 1

6.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5 6.3.1 Leaf and tuber soluble carbohydrate composition . . . . . . . . . . . 15 5 6.3.2 Starch and soluble carbohydrate concentration as a function of

duration from commencement of daily lighting . . . . . . . . . . . . 156 6.3.3 Starch and soluble carbohydrate concentration during plant

development 6.3.3.1 6.3.3.2 6.3.3.3 6.3.3.4

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . Tuber starch concentration . . . . . . . . . . . . . . . . Tuber soluble carbohydrate concentration . . . . . . .

Leaf starch and soluble carbohydrate concentration . 6.3.4 Carbohydrate and structural dry weight concentration as predictors

15 7 15 7 158 161 163

of growth and yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 6.4.1 Specific soluble carbohydrates and sample preparation . . . . . . . . 166 6.4.2 Diurnal and developmental changes in starch and soluble

carbohydrate concentration . . . . . . . . . . . . . . . . . . . . . . . . . 166 6.4.3 Tuber starch and structural dry weight changes with development . 169 6.4.4 Carbohydrate and structural dry weight concentration as predictors

of growth and yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 6.4. 5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

6.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . · 173

X

7 MANIPULATION OF IN VITRO SOURCE AND SINK STRENGTH, AND DRY MATI'ER PARTITIONING IN Zantedeschia 'Best Gold' . . . 18 0

7. 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . 18 0

7. 2 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 7. 2. 1 Germination media, media transfer and sucrose concentrations . . . 185 7. 2. 2 Manipulation of in vitro source and sink strengths . . . . . . . . . . 187

7. 3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 7. 3 . 1 Germination media, media transfer and sucrose concentrations . . . 189

7. 3 . 1 . 1 Germination . . . . . . . . . . . . . . . . . . . . . . . . . 189 7. 3 . 1. 2 Dry matter accumulation and partitioning . . . . . . . 189

7. 3 . 2 Manipulation of source and sink strengths . . . . . . . . . . . . . . . 19 2

7. 4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 7. 4 . 1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

7. 5 References

8 ECOLOGICAL AND HORTICULTURAL RELEVANCE, AND MECHANISMS OF CONTROL OF DRY MATI'ER ACCUMULATION AND PARTITIONING IN Zantedeschia 'Best Gold' - AN

205

INTEGRATIVE DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . 212

8. 1 Ecological relevance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

8. 2 Mechanisms of control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

8 .3 Horticultural relevance and consequences . . . . . . . . . . . . . . . . . . . . 218

8. 4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

xi

UST OF ABBREVIATIONS

a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . apparent photosynthetic quantum yield aw,A,L,u,TocT• • • • • • • • • • • • • • • • • • upper asymptote of factor under investigation

A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . leaf area.

flw ,A,r.,:u,T « T• • • • • • • • a measure of the starting size of the factor under investigation

BA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . benzyl ( lH-purin- 6-yl) amine

C ................................................ Celsius

cm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . centimetre 2 .

cm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . square centimetre CE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . controlled environment C02 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • carbon dioxide D1'EMP . . . . . . . . . . . . . . . . · . . . . . . . . . . . . . . . . . . . . . . day temperature g ................................................. grnm. GA3 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • gibberellic acid G.A"+7 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • gibberellin 4 and 7 h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . hour ha ................................................ hectare HPLC . . . . . . . . . . . . . . . . . . . . . . . . . high performance liquid chromatograph i.e. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (id est) that is "w .A.L.u,T or T• • • • • • • • rate constant of factor under investigation as a function of size kg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . kilogrnm. L . i. . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .leaf weight LAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .leaf area partitionmg L.AR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . leaf area ratio L WP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . leaf weight partitioning L WR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . leaf weight ratio loge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . natural logarithm Ls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . leaf starch dry weight LS . . . . . . . . . . . . . . . . . . . . . . . . . . . Linsmaier and Skoog organic additives m ................................................. metre m2

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • square metre m3 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • cubic metre

. mg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . milligrnm. min . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . minute ml . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . millilitre M . . · ................. .-............................. molar mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . millimetre MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Murashige and Skoog medium

Xll

n ..... number of observations in a sample

ng ..

nm .

N AR

N.B.

. ...................... ....... nanogram

. ....... nanometre

. . net assimilation rate

. (nota bene) note well

NTEMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . night temperature

P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . probability

Pa ..

pH . . Pmax . Pn .

PPF pp m

r

R .. r ..

RGR .

........................... Pascal

. . . . . . . . . . . . measure of acidity or alkalinity

. . maximum photosynthetic rate at saturating PPF

. . . net photosynthetic rate

. photosynthetic photon flux

. . . . parts per million . . . . . . . . . . . partial correlation

. . . . . . . . . . . . . respiration rate . . . . . . . . . . . . . . coefficient of determination

................... relative growth rate RLAER ....... . . ................ relative leaf area expansion rate

RLSWR ....... . . . . . . . . . . . . . . . relative leaf starch weight rate

RLWR ........ . . ....................... relative leaf weight rate

RWP s .. • ..

SAS I

s.e . .

SLA

str .

. . . . . . . . . . . . . . . . . . . . . . . � . . root weight partitioning ............................... second

.. Statistical Analysis System (statistical software)

. . . . . . . . . . . . . . . . . . . . . . . . . . . standard error of the mean

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . specific leaf area

. . . dry weight of structural material (i.e. , minus soluble sugars and starch)

t ............. ...................................... time

T .. T% .

tanh

Ts

Tstr .

TWP

j.tl ..

Jlm .

j.tmOl

. . . . . . . . . . . . . . . . . . . • . . . . time to commencement of tuber growth

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . tuber dry weight

. . . percentage tuber weight loss at the commencement of tuber growth

..................................... hyperbolic tangent

................................. tuber starch dry weight

. dry weight of tuber structural material (i.e., minus soluble sugars and starch)

. . . . . . . tuber weight partitioning

. . . . . . . . microlitre

. . . . . . . micrometre

. .......... micromole

viz. . . . . . . . . . . . . . . . . . . . . . . . . . . . (videlicet) namely

v/v ........................ ................ volume (mix ratio)

xiii

W . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . total plant dry weight

%LA ................................ percentage maximum leaf area

o 'S

0 .... .

JlP .. . .

. .. ... ns,, ,

angular distance on its meridian South of equator in degrees and minutes

. . . . . . . . . . . . . . . . . . . . . . . mathematical notation for an interval

. . . . . . . . difference between photosynthetic rate under saturating PPF

and photosynthetic rate under the growth PPF

unless otherwise stated, probability of a significant F value;

nonsignificant or significant at P = 0. 10, 0.05 , or 0.01 , respectively

NOTES ON CITATION FORMAT

With a view to publishing this thesis as a series of scientific papers in journals such as

those produced by the American Society for Horticultural Science (ASHS), the style of

literature citation follows that recommended by ASHS. The citation system used therefore

follows the Harvard system, and abbreviations for periodical titles are as suggested by

ASHS.

xiv

LIST OF TABLFS

Table 1 . 1

Table 1 .2

Table 1.3

Table 3.1

Table 3.2

I ' '

Table 3.3

Table 3.4

PAGE

Descriptive features of the species and subspecies of Zantedeschia

Spreng. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Average daily maximum, minimum, mean air, and minimum soil (8.00 am, at 10 cm), temperatures (C) during the winter (June to July), for sites of natural habitat of Zantedeschia aethiopica, Zantedeschia pentlandii and Zantedeschia rehlnannii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Average daily maximum, minimum, mean air, and minimum soil (8.00 am, at 10 cm), temperatures (C) during the summer (October to February) for sites of natural habitat of Zantedeschia aethiopica, Zantedeschia pentlandii

and Zantedeschia rehlnannii . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Duration of growth (days) until attainment of 7 5 % or more expansion of the first leaf of Zantedeschia 'Best Gold: at a range of temperatures, and high and low PPF regimes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5

Total plant relative growth rates (RGRw ± standard error), and associated rl, for plants of Zantedeschia 'Best Gold' grown at day/night temperatures of 22/16 C, at high and low PPF, in two CE rooms over two years . 5 7

Nonlinear least-squares parameter estimates, associated asymptotic standard error (s.e.), and mean square error values, from fitting the Gompertz function to lo� transformed total plant dry weight data for Zantedeschia

'Best Gold' grown at a range of temperatures, and under high and low PPF regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9

Nonlinear least-squares parameter estimates, associated asymptotic standard error (s.e.), and mean square error values, from fitting the logarithmic Gompertz function to lo� transformed total plant leaf area data for Zantedeschia 'Best Gold' grown at a range of temperatures, and under high and low PPF regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Table 3.6

Table 4. 1

Table 4.2

Table 4.3

Table 5. 1

Table 7.1

Table 7.2

Table 7.3

XV

Nonlinear least-squares parameter estimates, associated asymptotic standard error (s.e.), and mean square error values, from fitting the logarithmic Gompertz function to lo� transformed total plant leaf dry weight data for Zantedeschia 'Best Gold' grown at a range of temperatures, and under high and low PPF regimes . . . . . . . • . . . . . . • . . . . . . . . . . . . . . . 64

Leaf area (cm� at inflection point of the fitted total plant dry weight Gompertz curve of Zantedeschia 'Best Gold; grown at a range of temperatures, and high and low PPF regimes . . . . . . . . . . . . . . . 65

Parameters examined in the development of a mechanistic multiple regression model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Nonlinear least-squares parameter estimates, associated asymptotic standard error (s.e.), and mean square error values, from fitting the Gompertz function to loge transformed tuber dry weight data for Zantedeschia 'Best Gold' grown at a range of temperatures, under high and low PPF regimes ...................................... 94

Partial correlation matrix between TWP, L WP, NAR and RGRT at the inflection point of the Gompertz fit of tuber, dry weight curves of Zantedeschia 'Best Gold' grown under a range of environments . . . 103

Correlation between photosynthetic rate (Pn) and relative growth rate of total plant weight (RGRw) and tuber dry weight (RGRT) of Zantedeschia

'Best Gold' grown at six day/night temperatures and two PPF regimes, during two stages of development . . . . . . . . . . . . . . . . . . . . . 132

Dry matter accumulation and partitioning in seedlings of Zantedeschia

'Chromatella: as influenced by the presence of light or dark, and sucrose concentration in the growing medium . . . . . . . . . . . . . . . . . . . 191

Dry matter accumulation and partitioning in seedlings of Zantedeschia 'Best Gold: as influenced by temperature and sucrose concentration . . . . 193

Dry matter accumulation within the shoot of seedlings of Zantedeschia 'Best Gold: as influenced by temperature and sucrose concentration . . . . 194

xvi

Signifi�ce of trend analyses of increasing temperature and sucrose concentration on dry matter accumulation and partitioning in seedlings of Zantedeschia 'Best Gold' . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

.. Figure 1.1 '

Figure 1.2

Figure 1 .3

Figure 3.1

Figure 3.2

Figure 3.3

Figure 3.4

xvii

PAGE

Distribution of species in the genus Zantedeschia across the southern regions of Africa. (a) Z. odoraJa •, Z. jucunda e, and Z. pentlandii IIl, (b) Z. rehmannii [], (c) Z. albomaculata [l], and (d) Z. aethiopica El. Adapted from Letty (1973); Anon (1989); Perry (1989) .......... 6

Diagrammatic illustration of sympodial growth habit of a single primary shoot of Zantedeschia . . • . . . . . . . . . • . . . . . . . . . . . . . . . . . 19

Diagrammatic illustration of primary shoot of Zantedeschia, with secondary shoots arising from leaf axils . . . . . . . . . . . . . . . . . . . . . . . . . 19

Examples of total plant dry weight (logJ as a function of time, for Zantedeschia 'Best Gold� � indicates day of transfer to treatments . 54

Examples of relative growth rate (RGR.w) as a function of time, for Zantedeschia 'Best Gold� � indicates day of transfer to treatments . 55

Maximum value of RGRw as a function of temperature, for plants of Zantedeschia 'Best Gold' grown under high and low PPF regimes . � 56

Total plant dry weight (lo� fitted Gompertz curves) for Zantedeschia 'Best Gold' at a range of temperatures, under a high PPF regime. � indicates day of transfer to treatments . . . . . . . . • . . . . . . . . . . . . . . . . . 58

Figure 3.5 Total plant dry weight (log., fitted Gompertz curves) for Zantedeschia 'Best Gold' at a range of temperatures, under a low PPF regime. � indicates day of transfer to treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Figure 3.6 Lo� m�mum total plant dry weight (aw) as a function of temperature, for \

Zantedeschia 'Best Gold' under high and low PPF regimes. Fitted line for high PPF regime only . . . . . . . . . . . . . . . . . . . . . . . . . . � . . . 60

Figure 3. 7 Interrelation between the rate of decline of RGRw as a function of plant size

(Kw), and temperature, for Zantedeschia 'Best Gold' under high and low

PPF regimes. Fitted line for low PPF only . . . . . . . . . . . . . . . . 61

xviii

f2iii!e 3. 8 Fitted logarithmic Gompertz curves and mean data of total plant leaf area

(log.) as a function of time, for Zantedeschia 'Best Gold' at a range of

temperatures, under a high PPF regime . . . . . . . . . . . . . . . . . . . 6 2

-� 3. 9 Fitted logarithmic Gompertz curves and mean data of total plant leaf area

(log.) as a function of time, for Zantedeschia 'Best Gold' at a range of temperatures, under a low PPF regime . . . . . . . . . . . . . . . . . . . 6 2

F.tgUI'e 3. 1 0 Lo� maximum total plant leaf area (a.J as a function of temperature, for Zantedeschia 'Best Gold' under high and low PPF regimes. Fitted line for high PPF regime only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5

igure 3. 11 Parameter {JA as a function of temperature, for Zantedeschia 'Best Gold'

under high and low PPF regimes. Fitted line for low PPF only . . . 66

FigUre 3. 12 Interrelation between the rate of decline of RLAER8 (K.J and temperature,

for Zantedeschia 'Best Gold' under high and low PPF regimes . . . . 67

Fjgure 3. 1 3 RGRw as a function of RLAER, for Zantedeschia 'Best Gold' grown under two PPF regimes and six temperatures . . . . . . . . . . . . . . . . . . . 69

' .

Figure 3: 1 4 RGRw as a function of NAR, for Zantedeschia 'Best Gold' grown under two PPF regimes and six temperatures . . . . . . . . . . . . . . . . . . . . . . 69

Figure 3. 1 5 RGRw as a function of LAP , for Zantedeschia 'Best Gold' grown under two PPF regimes and six temperatures . . . . . . . -. . . . . . . . . . . . . . . 69

Figure 3. 1 6 RGRw as a function of LWP, for Zantedeschia 'Best Gold' grown under two PPF regimes and six temperatures . . . . . . . . . . . . . . . . . . . . . . 69

Figure 4 . 1 Shoot, tuber, root and total dry weight per plant of Zantedeschia 'Best Gold' plants grown at 2 5 C under high PPF. n=6 or 1 2 . . . . . . . . . . . . 89

Figure 4 . 2 Tuber dry weight (expressed as logJ of Zantedeschia 'Best Gold' plants grown under high or low PPF at 1 6 or 2 8 C . . . . . . . . . . . . . . . . 90

figure 4 . 3 Time to commencement of tuber growth (tJ as a function of temperature for Zantedeschia 'Best Gold: grown under high and low PPF regimes . . 91

xix

Figure 4.4 Extent of tuber weight loss (T ") at the time of commencement of tuber

growth, as a function of temperature, for Zantedeschia 'Best Gold: grown

under high and low PPF regimes . . . . . . . . . . . . . . . . . . . . . . . 92

Figure 4.5 Fitted Gompertz curves and mean data points of lo� tuber dry weight as a

function of time, for Zantedeschia 'Best Gold' at a range of temperatures,

under high PPF regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Figure 4.6 Fitted Gompertz curves and mean data points of loge tuber dry weight as a

function of time, for Zantedeschia 'Best Gold' at a range of temperatures,

under a low PPF regime . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Figure 4.7 Loge maximum tuber dry weight (aT) as a function of temperature, for

Zantedeschia 'Best Gold' under high and low PPF regimes . . . . . . . 95

Figure 4.8 RGRT as a function of temperature, for plants of Zantedeschia 'Best Gold:

grown under high and low PPF regimes. (N.B., line for low PPF excludes

28 C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Figure 4.9 Proportion of daily increment in total weight partitioned to the tuber (TWP)

as a function of time, for Zantedeschia ·'Best Gold: at a range of

temperatures, under a high PPF regime . . . . . . . . . . . . . . . . . . . 98

Figure 4.10 Proportion of daily increment in total weight partitioned to the tuber (TWP)

as a function of time, for Zantedeschia 'Best Gold: at a range of

temperatures, under a low PPF regime . . . . . . . . . . . . . . . . . . . 98

Figure 4. 1 1 Proportion of daily increment in total weight partitioned to the tuber (TWP),

as a function of time, for Zantedeschia 'Best Gold: grown under high and

low PPF regimes at 13 or 28 C . . . . . . . . . . . . . . . . . . . . . . . . 99

Figure 4.12 Proportion of daily increment in total weight partitioned to the tuber (TWP),

as a function of temperature, for zantedeSchia 'Best Go1d' undet high and

low PPF regimes . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . 100

Figure 4.13 Proportion of daily increment in total weight partitioned to leaf (LWP) as

a function of temperature, for Zantedeschia 'Best Gold' under high and low

PPF regimes. (N.B., line for high PPF excludes 13 C) . . . . . . . . 101

XX

14 Net assimilation rate (NAR) as a function of temperature, for plants of �............

Zantedeschia 'Best Gold; grown under high and low PPF regimes. (N.B. , line for high PPF regime excludes 13 C) . . . . . . . . . . . . . . • . . 102

lf!i� 4. 15 Relative growth rate of the tuber (RGRT) as a function of daily partitioning to the tuber (IWP) for Zantedeschia 'Best Gold' grown under high and low

PPF regimes at all temperatures . . . . . . . . . . . . . . . . . . . . . . 104

� 4. 16 Relative growth rate of the tuber (RGRT) as a function of daily partitioning to the leaf (L WP) under high and low PPF regimes, at all temperatures. Jjne is for low PPF regime at temperatures � 16 C . . . . . . . . . . 104

FJgUie 4. 17 Relative growth rate of the tuber (RGRT) as a function of net assimilation rate (NAR) under high and low PPF regimes, at all temperatures. Line is for high PPF regime at temperatures � 16 C . . . . . . . . . . . . . . 105

�JgUie 5.1 Net photosynthetic rate (Pn) as a function of individual leaf area expansion, at selected temperature and PPF regimes. Mean values ± se. , n=6, cubic spline fit. Arrows represent 75% maximum leaf area . . . . . . . . . 122

tF"IgUre 5.2 Photosynthetic rate (Pn) as a function of duration from commencement of daily lighting, at selected temperature regimes and high PPF. Mean values ± se. , n=6. Broken lines indicate limits of diurnal temperature changeovers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

�

�Figure 5.3 Photosynthetic rate (Pn) per unit leaf area (a)_ and (b) , and per unit leaf weight (c) and (d) , as a function of photosynthetic photon flux (PP F), for plants of Zantedeschia 'Best Gold' grown at day temperatures of 16, 22 and 28 C, under high (a) and (c), or low (b) and (d), PPF regimes. n=6 or 18, function = equation 5 . 1 . . . . . . . . . . . . . . . . . . . . . . . . . 125

Figure 5.4 Maximum photosynthetic rate (Pmax) per unit leaf area as a function of day temperature: for plants of Zantedeschia 'Best Gold' grown under high and low PPF. Vertical bars = 2 x standard error . . . . . . . . . . . . . 126

Figure 5.5 Maximum photosynthetic rate (Pmax) per unit leaf weight as a function of day temperature, for plants of Zantedeschia 'Best Gold' grown under high and low PPF. Vertical bars = 2 x standard error . . . . . . . . . . 126

xxi

Quantum yield (ex) per unit leaf area as a function of day temperature, for plants of Zantedeschia 'Best Gold' grown under high and low PPF. Vertical bars = 2 x standard error . . . . . . . . . . . . . . . . . . . . 127

Figure 5.7 Quantum yield (ex) per unit leaf weight as a function of day temperature, for plants of Zantedeschia 'Best Gold' grown under high and low PPF. Vertical bars = 2 X standard error . . . • . . . . . . . . . . . . . . . . 127

�Figure 5 .8 Difference (MJ) between P JIMX and Par- per unit leaf area, for plants of Zantedeschia 'Best Gold' grown at a range of temperatures, under high and

�

'·

low PPF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Figure 5.9 Difference (MJ) between P JIMX and Par- per unit leaf weight, for plants of t Zantedeschia 'Best Gold' grown at a range of temperatures, under high and

low PPF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ! • • 128

�Figure 5 . 10 Photosynthetic rate (Pn), per unit leaf area, of the most recently expanded ·L

leaf as a function of time, for Zantedeschia 'Best Gold' grown at a range of day/night temperatures under high and low PPF regimes. (a) 16/10 C (b) 22/10 C (c) 22/16 C (d) 28/16 C (e) 28/22 C (f) 28/28 C. Vertical bars = 2 X standard error, arrows indicate commencement of tuber growth under high (H) and low (L) PPF . . . . . . . . . • . . . . . . . . . . . . 130

Figure 5. 1 1 Photosynthetic rate (Pn), per unit leaf weight, of the most recently expanded leaf as a function of time, for Zantedeschia 'Best Gold' grown at a range of day/night temperatures under high and low_ PPF regimes. (a) 16/10 C (b) 22/10 C (c) 22/16 (d) 28/16 C (e) 28/22 C (f) 28/28 C. Vertical bars = 2 x standard error, arrows indicate commencement of tuber growth under high (H) and low (L) PPF . • . . . . . . . . . . . . . . . . . . . . . . . . 131

Figure 6. 1 Soluble carbohydrate concentration of mature leaves of Zantedeschia 'Best Gold' determined either immediately after harvest (fresh) or after vacuum drying (dry). Mean values ± se., n=3 . . . . . . . . . . . . . . . . . 155

Figure 6.2 Solub!e carbohydrate concentration of tubers of Zantedeschia 'Best Gold' determined either immediately after harvest (fresh) or following vacuum drying (dry). Mean values ± se. , n=3 . . . . . . . . . . . . . . . . . 155

xxii

Figure 6.3 Photosynthetic rate (Pn) and foliar carbohydrate concentration, as a function of duration of daily lighting, at 28/22 C under high PPF. Mean values ± se., n = 3. Broken lines indicate limits of diurnal environmental chan.geovers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

.;Figure 6. 4 Tuber carbohydrate concentration as a function of duration of daily lighting

at 28/22 C under high PPF. Mean values ± se., n=3. Broken lines

indicate limits of diurnal environmental chan.geovers . . . . . . . . . . 156

Figure 6.5 Total, structural and starch tuber dry weight QogJ, as a function of time,

of Zantedeschia 'Best Gold' plants grown at 25 C under high PPF.

� indicates day of transfer to treatment environment . . . . . . . . . . 157

Figure 6.6 Minimum tuber starch concentration as a function of temperature, for plants

of Zantedeschia 'Best Gold' grown under high and low PPF regimes.

Mean values ± se., n =4 . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Figure 6. 7 Carbohydrate concentration of the tuber as a function of time, for

Zantedeschia 'Best Gold' grown at three temperatures under high and low

PPF regimes. (a) 13 C, high PPF (b) 1 3 C, low PPF (c) 19 C, high PPF

(d) 19 C, low PPF (e) 25 C, high PPF (f) 2 5 C, low PPF. Mean values

± se., n=4, � indicates commencement of tuber growth . . . . . . . 159

Figure 6. 8 Tuber starch dry weight as a function of tuber structural dry weight. Low

PPF before (-D-), and both high and low PPF after (-0-), the

commencement of tuber growth, for plants grown at three temperatures and

two PPF regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

Figure 6.9 Relative growth rate (RGR) of tuber starch and tuber structural dry weight

as a function of time, for Zantedeschia 'Best Gold' grown at three temperatures under high and low PPF regimes. (a) 19 C, high PPF

(b) 19 C, low PPF (c) 25 C, high PPF (d) 25 C, low PPF . . . . . . 162

Figure 6.10 Starch concentration of first leaf, as a function of temperature, for plants of

Zantedeschia 'Best Gold' grown under high and low PPF regimes. Mean

values ± se., n =4 ...... ................ . ·. . . . . . . 16 3

xxiii

Figure 6.11 Soluble carbohydrate concentration · of first leaf, as a function of

temperature, for plants of Zantedeschia 'Best Gold' grown under high and

low PPF regimes. Mean values ± se. , n=4 .............. 163

Figure 6.12 Carbohydrate concentration of mature leaves as a function of time, for

Zantedeschia 'Best Gold' grown at three temperatures under high and low

PPF regimes. (a) 13 C, high PPF (b) 13 C, low PPF (c) 19 C, high PPF

(d) 19 C, low PPF (e) 2 5 C, high PPF (f) 2 5 C, low PPF. Mean values

± se. , n =4, � indicates commencement of tuber growth . . . . . . . 165

Figure 7.1 Diagrammatic summary of germination and transfer treatment media used

for seedlings of Zantedeschia 'Chromatella' . . . . . . . . . . . . . . . 18 7

Figure 7.2 Surface response curves illustrating the influence of increasing temperature

and sucrose concentration on the dry matter accumulation and partitioning

in seedlings of Zantedeschia 'Best Gold� (a) Total dry weight, (b) Tuber

dry weight, (c) Shoot dry weight, and (d) Proportion of total dry weight in

the tuber . . . . . . . . . . . . . . . . · . . . . . . . . . . . . . . . . . . . . . 196

Figure 7.3 Surface response curves illustrating the influence of increasing temperature

and sucrose concentration on the number of (a) shoots and (b) leaves in

seedlings of Zantedeschia 'Best Gold' . . . . . . . . . . . . . . . . . . . 19 7

xxiv

LIST OF PLATES

Plate 1. 1

Plate 1. 2

Plate 3. 1

Plate 7. 1

Plate 7. 2

Plate 7. 3

PAGES

Dissection of spathe to reveal complete separation of (m) male and (f)

female flowers on spadix of the group 2 selection 'Best Gold' (right),

compared with being interspersed on lower part of spadix in the group 1

specie Z. aethiopica (left). (a) region of dark pigmentation at the base of

the spathe of 'Best Gold' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Flowering sized tuber of a group 2 selection indicating examples of

(a) dominant bud, (b) developed axillary bud, and (c) undeveloped axillary

bud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Harvested plant of Zantedeschia 'Best Gold' illustrating components

measured. (a) shoot (sheath leaves, petioles and apex, (b) exposed leaves,

(c) tuber, (d) roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Germinated seedling of Zantedeschia 'Chromatella' after being excised from

the cotyledon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5

Seedlings of Zantedeschia 'Chromatella' after 2 9 weeks of cultivation in

vitro at a range of sucrose concentrations in either the dark (upper) or light

(4 5 JLmoi-m-2·s-1 PPF) (lower) . . . . . . . . . . . . . . . . . . . . . . . . 19 0

Tubers from seedlings of Zantedeschia 'Best Gold' after 24 weeks of growth

in vitro, at a range of temperatures and sucrose concentrations. N.B. shoots

and roots removed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197